Nasal mask



FIG. 1 is a perspective view of a nasal mask, showing my new design, the broken line showing is for illustrative purposes only and forms no part of the claimed design;

FIG. 2 is an enlarged perspective view of the nasal mask;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a left side elevational view thereof with the right side elevational view being a mirror image of the left side elevational view;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof. 

The ornamental design for a nasal mask, as shown and described. 